Pain assessment is a significant challenge in critically ill adults, especially those who are unable to communicate their pain level. Unfortunately in critical care, many factors alter verbal communication with patients including tracheal incubation, reduced level of consciousness, sedation, and administration of paralyzing drugs. Patients who are unable to report pain are at even greater risk of inadequate pain management. The need for optimal pain assessment in adult critical care settings is essential since it has been reported that nurses have been known to rate pain lower than the patient. National pain guidelines mandate evaluation of both physiological and behavioral response to pain in patients who are unable to communicate. In addition, the Agency for Healthcare Research and Quality and the Joint Commission for the Accreditation of Health Organizations (JCAHO) require that pain be assessed in "all patients" and it be considered the "fifth vital sign." JCAHO recommends that tools to evaluate pain should be specific to the age and disease state of the patient and to the site of pain. The first step in providing adequate pain relief for patients is systematic and consistent assessment and documentation of pain. Identification of the optimal pain scales for non-communicative (cognitively impaired, sedated, paralyzed or mechanically ventilated) patients have been the focus of several studies. To date, however, no one tool is universally accepted for use in the non-communicative patient. A common component of behavioral pain tools is evaluation of facial behaviors. Although use of facial expression is an important behavioral measure of pain intensity, precise and accurate methods for interpreting the facial expression of pain has not been empirically evaluated in critically ill, non-communicative patients. Therefore the specific aim of this prospective study is to describe facial expression in non-communicative critically ill patients experiencing pain. A secondary aim of this study is to describe the effect of age, diagnosis (medical vs. surgical patients), incubation status, severity of Illness, and level of sedation on facial expression during pain. Understanding facial expressions will assist in the development of strategies to enhance pain evaluation and management and eventually foster better decision-making among nurses. Specifically, these data will provide empirical evidence that will enable us to use facial expressions accurately in assessment tools that are appropriate, practical, reliable, and valid across patient populations. LAY LANGUAGE: Changes in facial expression are often used to evaluate pain in critically ill patients who can not communicate verbally. This study will evaluate the type of facial expressions seen in these patients to improve nursing assessment and management of pain.